Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$34.51	8.423%	$37.4168	$37.42	$37.40	$37.40
Purchase #2	$65.39	10.494%	$72.252	$72.25	$72.25	$72.30
Purchase #3	$21.46	12.179%	$24.0736	$24.07	$24.05	$24.10
Purchase #4	$94.84	9.152%	$103.5198	$103.52	$103.50	$103.50
Purchase #5	$97.50	7.133%	$104.4547	$104.45	$104.45	$104.50
Purchase #6	$133.52	10.465%	$147.4929	$147.49	$147.50	$147.50
Purchase #7	$127.62	5.486%	$134.6212	$134.62	$134.60	$134.60
7 purchase totals =	$574.84		$623.8310	$623.82	$623.75	$623.90